Field of the Invention
The present invention relates to a twisted nematic (TN)-mode liquid crystal display (LCD) apparatus having a liquid crystal layer with coexistent regions within one pixel and a compensation layer, capable of operating excellently in terms of visual angle and contrast.
A first prior art TN-mode LCD apparatus includes two electrodes with first and second oriented layers coated thereon and a twisted-mode type liquid crystal layer sandwiched by the electrodes. In this case, a micro-rubbing technique is introduced in a plurality of regions of one pixel. For example, a rubbing direction in one region of the first oriented layer is opposite to a rubbing direction in another region of the first oriented layer. Also, a rubbing direction in one region of the second oriented layer is opposite to a rubbing direction in another region of the second oriented layer. As a result, the orientation of liquid crystal molecules in one region of the liquid crystal layer is different from the orientation of liquid crystal molecules in another region of the liquid crystal layer, so that one pixel is divided into a plurality of sub-pixels, thus improving the visual angle characteristics as a whole (see JP-A-63-106624). This will be explained later in detail.
In the first prior art apparatus, however, since each pixel is divided into sub-pixels with different twisted directions of liquid crystal orientation and different directions of tilt angles of liquid crystal molecules, light transmittance at an inclined visual angle is not reduced, so that a so-called "floating white" phenomenon occurs when a voltage is applied to show "black" in one pixel. Thus, a high contrast cannot be obtained at a wide visual angle.
In a second prior art TN-mode LCD apparatus, rubbing directions of first and second oriented layers are uniform within one pixel, so that one pixel is not divided into a plurality of sub-pixels. That is, the rubbing direction of the first oriented layer is orthogonal to the rubbing direction of the second oriented layer, so that a twisted angle of liquid crystal orientation is 90.degree.. Instead of this, a biaxial phase difference compensation layer is provided between a polarization plate and a transparent substrate. Thus, the refractive anisotropic characteristics to inclined incident light are regulated to realize wide visual angle characteristics. Particularly, optical characteristics of liquid crystal molecules that are rising as a voltage is applied can be improved (see JP-A-7-120746). This will also be explained later in detail.
In the second prior art apparatus, however, since the direction of tilt angles of liquid crystal molecules differs from minute region to minute region, a satisfactory effect cannot be expected.